Cognitive disorders, i.e. impairments of memory and learning processes, have a significant detrimental effect on the quality of life of patients affected by it. Clinically recognized cognitive disorders vary from mild cognitive impairment through to dementias of varying severity.
Mild cognitive impairment (“MCI”) is a transition stage between the cognitive changes of normal aging and the more serious problems caused by Alzheimer's disease. The amnestic subtype of MCI, which have been linked to development of Alzheimer's disease, significantly affects memory.
Dementia is a clinically recognised broad-spectrum syndrome consisting of degrees of loss of cognitive abilities. Dementia can be one of many symptoms of various neurological diseases or the main abnormality associated with the disease, as it is the case in Alzheimer's disease. (Adams and Victor's, Principle of Neurology, 7th ed.)
Most common causes of dementia include: cerebral atrophy associated with Alzheimer's disease, Lewy-bodies disease, frontotemporal lobar degeneration, Pick's disease; vascular narrowing or blockage in the brain (i.e. vascular dementia also known as multi-infarct dementia); Huntington's disease, Parkinson's disease; head trauma; HIV infection or Down's syndrome.
Currently there only several medications that have been shown to afford at most a modest transient benefit to the patients. Cholinesterase inhibitors (anticholinesterases), such as donepezil (Aricept®), galantamine (Razadyne®, Razadyne ER®, Reminyl®, Nivalin®) and rivastigmine tartrate (Exelon®) have been show to be efficacious in mild to moderate Alzheimer's disease dementia. Exelon® has recently been approved for the treatment of mild to moderate dementia associated with Parkinson's disease. Memantine NMDA receptor antagonists are the first approved Alzheimer's disease medication acting on the glutamatergic system (Axura®, Akatinol®, Namenda®, Ebixa®). These drugs however have side effects which in some cases lead to discontinuation of the therapy.
With the increase in the life span and general aging of the population there is a need to develop drugs which could delay or alleviate the cognitive function in aging patients.